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	<title>three.js - gpu particle system</title>
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<body>

	<div id="container"></div>
	<div id="info">
		<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> - GPU particle system plugin by <a href="http://charliehoey.com">Charlie Hoey</a>.
	</div>

	<script src="../build/three.js"></script>
	<script src="./js/controls/TrackballControls.js"></script>
	<script src="./js/libs/dat.gui.min.js"></script>
	<script src="./js/libs/stats.min.js"></script>
	<script src="./js/GPUParticleSystem.js"></script>

	<script>
		var camera, tick = 0,
			scene, renderer, clock = new THREE.Clock(),
			controls, container, gui = new dat.GUI( { width: 350 } ),
			options, spawnerOptions, particleSystem;

		var stats;

		init();
		animate();

		function init() {

			//

			container = document.getElementById( 'container' );

			camera = new THREE.PerspectiveCamera( 28, window.innerWidth / window.innerHeight, 1, 10000 );
			camera.position.z = 100;

			scene = new THREE.Scene();

			// The GPU Particle system extends THREE.Object3D, and so you can use it
			// as you would any other scene graph component.	Particle positions will be
			// relative to the position of the particle system, but you will probably only need one
			// system for your whole scene

			particleSystem = new THREE.GPUParticleSystem( {
				maxParticles: 250000
			} );

			scene.add( particleSystem );

			// options passed during each spawned

			options = {
				position: new THREE.Vector3(),
				positionRandomness: .3,
				velocity: new THREE.Vector3(),
				velocityRandomness: .5,
				color: 0xaa88ff,
				colorRandomness: .2,
				turbulence: .5,
				lifetime: 2,
				size: 5,
				sizeRandomness: 1
			};

			spawnerOptions = {
				spawnRate: 15000,
				horizontalSpeed: 1.5,
				verticalSpeed: 1.33,
				timeScale: 1
			};

			//

			gui.add( options, "velocityRandomness", 0, 3 );
			gui.add( options, "positionRandomness", 0, 3 );
			gui.add( options, "size", 1, 20 );
			gui.add( options, "sizeRandomness", 0, 25 );
			gui.add( options, "colorRandomness", 0, 1 );
			gui.add( options, "lifetime", .1, 10 );
			gui.add( options, "turbulence", 0, 1 );

			gui.add( spawnerOptions, "spawnRate", 10, 30000 );
			gui.add( spawnerOptions, "timeScale", - 1, 1 );

			//

			stats = new Stats();
			container.appendChild( stats.dom );

			//

			renderer = new THREE.WebGLRenderer();
			renderer.setPixelRatio( window.devicePixelRatio );
			renderer.setSize( window.innerWidth, window.innerHeight );
			container.appendChild( renderer.domElement );

			//

			controls = new THREE.TrackballControls( camera, renderer.domElement );
			controls.rotateSpeed = 5.0;
			controls.zoomSpeed = 2.2;
			controls.panSpeed = 1;
			controls.dynamicDampingFactor = 0.3;

			window.addEventListener( 'resize', onWindowResize, false );

		}

		function onWindowResize() {

			camera.aspect = window.innerWidth / window.innerHeight;
			camera.updateProjectionMatrix();

			renderer.setSize( window.innerWidth, window.innerHeight );

		}

		function animate() {

			requestAnimationFrame( animate );

			controls.update();

			var delta = clock.getDelta() * spawnerOptions.timeScale;

			tick += delta;

			if ( tick < 0 ) tick = 0;

			if ( delta > 0 ) {

				options.position.x = Math.sin( tick * spawnerOptions.horizontalSpeed ) * 20;
				options.position.y = Math.sin( tick * spawnerOptions.verticalSpeed ) * 10;
				options.position.z = Math.sin( tick * spawnerOptions.horizontalSpeed + spawnerOptions.verticalSpeed ) * 5;

				for ( var x = 0; x < spawnerOptions.spawnRate * delta; x ++ ) {

					// Yep, that's really it.	Spawning particles is super cheap, and once you spawn them, the rest of
					// their lifecycle is handled entirely on the GPU, driven by a time uniform updated below

					particleSystem.spawnParticle( options );

				}

			}

			particleSystem.update( tick );

			render();

			stats.update();

		}

		function render() {

			renderer.render( scene, camera );

		}

	</script>
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